Ing. Ivana Beshajová Pelikánová, Ph.D.

Thin film layers are used in a wide range of fields (microchips, solar cells, etc.)because of the high dependency of their properties on the thickness of the layer. It is important to know how to achieve different thickness and quality of the layers by changing conditions of deposition. Samples of oxide thin film layers were prepared by magnetron sputtering. Two different materials were used - aluminum oxide and zinc oxide. Effect of different conditions (time and power of plasma)during the deposition was observed. The samples were evaluated from a few different points of view. Firstly, the thickness and capacity of each layer were measured. Thickness was also calculated from capacity and then compared to measured values. As expected, thickness increased with increasing time of deposition and with the increasing power of plasma during the deposition. Detail images of the layers were captured by an optical microscope and these images were processed in order to measure grain size. Average grain size was increasing with higher power during the deposition.

The work is focused on topic of dielectrics layers prepared by thin film layer technology, specifically by sputtering. Set of samples of thin film capacitors was prepared. Samples differ by different conditions of preparation of dielectric layer. Dielectric layers were deposited by sputtering of Al2O3on glass substrate. The measured parameters were the electrical capacity and thickness of the dielectric layer. Thickness was obtained with help of device using the stylus method. The main evaluated parameters are the capacity and thickness of thin film capacitors in dependence on the deposition process conditions–plasma power and deposition time.

Purpose The attack angle of stencil printing squeegees with different geometries was analysed using finite element modelling. Design/methodology/approach A finite element model (FEM) was developed to determine the attack angle during the stencil printing. The material properties of the squeegee were included in the model according to the parameters of steel AISI 4340, and the model was validated by experimental measurements. Two geometric parameters were investigated; two different unloaded angles (45° and 60°) and four overhang sizes of the squeegee (6, 15, 20 and 25 mm). Findings It was found that the deflection of the blade is nearly homogenous along the length of the squeegee. This implies that the attack angle does not change significantly along the squeegee length. The results showed significant differences between the initial and the attack angle. For example, the angle of the squeegee with 15 mm overhang size and with 60° initial angle decreased by more than 5° for a specific squeegee force of 0.3 N/mm; resulting in an attack angle of 53.4°. Originality/value The attack angle during the printing is considerably lower than the initial angle as a result of the printing force. The papers, which were dealing with the numerical modelling of the stencil printing presumed that the squeegees were having their initial angle. This could have led to invalid numerical results. Therefore, we decided to investigate the attack angle during stencil printing for squeegees with different initial geometries to enhance the numerical modelling of stencil printing.

The work focuses on the problematic of thin layers prepared by the method of vacuum evaporation. The relationship between properties of deposited aluminium thin film layer and settings of starting parameters of deposition process was analysed. The theoretically calculated thickness of layers was compared with measured values of thickness. Influence of oxide layer that grows on surface aluminium layer was discussed too.

The article concern with the topic of thick-film structures prepared by screen printing. Work is focused on analysis the influence of different types of polymer paste and preparation technology of layer on the pattern geometry. Set of samples of test structure with different sizes and shapes were printed on ceramics substrates. Measured parameters were the electrical resistance and the dimensions of the layers. Deviations from the theoretical width values for each type of paste were analyzed and compared. The path width was measured by optical microscope and the thickness of the layers by the stylus method.

Mechanical stress act on solder joints during transport, function and storage of the electronic equipment. Therefore, the knowledge of solder joints resistance against it is very useful. This article deals with comparison of mechanical resistance of SnCu0,7 and Sn42Bi58 solder alloys. The experiments were based on two PCBs (smaller and larger one, with soldering pads designed according to commonly used chip package) which were soldered together. Surface finishes of soldering pads were OSP, ENIG and HASL. Mechanical test were based on sharp tip, which were driving between two PCBs. From overall point of view a slightly better results were achieved for Sn42Bi58 solder alloy. Additionally the thicknesses of intermetallic layers were compared and voids frequency inside solder joints were inspected.

This paper focuses to the problematic of thin film metal layers. The samples prepared by vacuum evaporation of thin film meander-shaped aluminium layers were analysed. Electrical resistance and thickness of layer were included in the measured parameters. We evaluated these parameters in dependence of the volume of the source material, i.e., an aluminium wire. We observed a certain variance in measured values in a repeated experiment with a constant amount of the originating material. Sets of measured values were processed by statistical methods, namely histogram and Shapiro-Wilk normality test. We observe some interesting facts from the analysed data that can give us information about the influence of the evaporation process on the resulting properties of the layer.

Mechanical properties of solder joints have influence on reliability of electronic products. Therefore the knowledge of the mechanical behavior of solder joints is very important. This article deals with comparison of mechanical properties of solder joints prepared with conventional soldering methods and ultrasonic soldering methods. Material for samples preparation was based on two PCB (material FR4) with soldering pads which were soldered together. As solder alloy was used Sn965Ag3Cu0.5 for convention soldering method and active soldering alloy for ultrasound soldering. The mechanical resistance, changes according to used surface finishes the highest share strength, have been achieved for solder joints which ware prepared by ultrasonic soldering on pads with copper surface finish, worst results were achieved for pads with ENIG and HASL surface finishes.

For surface dielectric barrier discharge in air, we examined the effect of titanium dioxide on various regions of the active electrode on the electrical parameters of discharge, on its emission spectra, and for demonstration of the obtained results also on the concentration of ozone produced by the discharge. We used the active electrode in the form of nine interconnected parallel strips and a square counter electrode. The TiO2 layer covered either only the strips, the region between the strips, or all active electrode. As reference discharge we used the discharge without any layer of TiO2. We found that direct application potential has a version when the strips of the active electrode are covered with a layer of TiO2, because the concentration of ozone produced by the discharge is the highest in all investigated cases. This finding could therefore be used for construction of more efficient ozone generators.

This contribution introduces Failure Mode and Effect Analysis (FMEA) method applied to sputtering process. A model based paradigm is used for executing the FMEA method. The Authors employ this approach for increasing its efficiency and productivity. This work builds on the achievements resulting from the previous works concerning applying the Model Based FMEA method for the technological processes and products. In this article we present a knowledge model of sputtering process as well as meta-model of process generally. Finally, the report of potential defects, causes, consequences and provisions for investigating sputtering process in the FMEA sheet form is presented.

The work is focused on properties of paste materials for electronics. Soldering pastes and pastes for screen printing were tested. The dynamic viscosity dependencies of pastes were analyzed. Viscosity of paste strongly affected the result of technological process. Viscosity is changed with temperature. Mentioned pastes belong to non Newtonian fluids. That means that viscosity of pastes is changed with shear rate too. Viscosity dependence on temperature increasing from room temperature to 50°C approximately was measured for chosen samples. Differences between viscosity of paste at room temperature and viscosity at storage temperature in refrigerator were determined too. Dial viscometer HBT type was used for viscosity measurement. Viscometer was equipped by measuring system with geometrical configuration cone – plate and system with standard disc spindle.

This article is focused on comparing of different assembly methods, particularly stencil printing and dispensing paste deposition and compares lead and lead-free solder pastes with one-component and two-component epoxy based electrically conductive adhesives. The evaluation method is based on resistance measurement after accelerated stress tests. The aging was conducted using automatic mechanical cyclic stress machine tester and joint resistance to environment was tested using long term temperature straining and combined humidity and temperature straining. Shear strength measurement was done in order to determine mechanical stability of the connection.

This contribution introduces Failure Mode and Effect Analysis (FMEA) method applied for screen printing process. A model based paradigm is used for executing FMEA method. The Authors employ this approach for increasing its efficiency and productivity. This work builds on the achievements resulting from the previous works concerning applying the Model Based FMEA method for technological processes and products. In this article we present a knowledge model of screen printing process as well as meta-model of process generally. Finally, the report of potential defects, causes, consequences and provisions for investigated screen printing process in the FMEA sheet form is presented.

Solder paste printing is one of the most important steps in the surface mount technology, which has high influence on the resulting quality of solder joints. To achieve a good joint quality, the solder paste should have specific properties like adhesion, viscosity, size of the solder alloy particles, amount of flux etc. This paper is focused on the measurement of the solder paste viscosity during its tempering and aging with possibility of regeneration of solder paste properties by jelly flux. Three types of solder pastes were used in the experiment: Sn95.5Ag4Cu0.5, Sn96.5Ag3Cu0.5 and Sn62Pb36Ag2. Viscosity of solder paste is measured from storing temperature to the ambient temperature. Aging of solder pastes is made in ambient atmosphere. Regeneration of solder paste properties after aging was done by adding of jelly flux Amtech 4300/LF-4300-TF. The viscosity of pure solder paste before aging, pure solder paste after aging and solder paste after aging regenerated by jelly flux was measured by rotation viscometer Brookfield Synchroelectric Viscometer, model HBT. The article describes if the addition of jelly flux to the aged solder pastes regenerates their properties.

The work is concerned about thin film prepared by methods of physical vapor deposition. The thin film aluminum layers were prepared, measured and analyzed. Tested layers were deposited by technology of sputtering from aluminum target on glass substrate. The properties of thin film layers such as electrical resistance and thickness were measured. The thickness of layer was evaluated from scanned profile of sample surface by stylus method. Obtained experimental data were investigated in dependence to parameters of depositing process. The different conditions of sputtering process used for sample preparation were set up by combinations of power of plasma and time of deposition process.

Surface mount technology has many problems during production. One of them is a problem called tombstone effect. Tombstone effect is a well known phenomenon, when one end of the component (commonly small passive devices such as resistor or capacitor), rises up out of the solder pad and breaks conductive contact. This article focus on the problem with tombstone effect, in concrete in this article we studied the influence of type of reflow technology and type of surface finish on tomb stone effect. In our experiments three types of reflow technologies, three sizes of SMD components, one type of solder paste and three types of surface finishes were used.

Solderability is an essential characteristic of soldering system in electronics industry. Molten solder must show good solderability, on the substrate surface to ensure a good quality of solder joints. Solderability degree depends on many factors such as type of solder alloy together with type of flux and material substrate, type of atmosphere (ambient, inert – nitrogen), temperature of solder alloy etc. In our article we focus on dependence of solder alloys solderability on different thermal capacity. For measurement we used a wetting balance method. Wetting balance method is able to assess qualitatively the wetting of liquids (molten solders) on various substrates. Method measures wetting force during the test specimen is immersed into the liquid (into the molten solder bath). Material base of our experiments was carried on three types of solder alloys (Sn99Cu1, Sn95.5Ag3Cu0.7 and Sn63Pb37), three different thermal capacities of the samples. Different thermal capacity of the samples is given by different diameter of the samples, when we used copper wire with diameters 0.3 mm, 0.4 mm and 0.7 mm.

The work is focused on investigation of influence screen printing parameters on variance in defined geometry of thick film layer. The thick film structures were deposited on substrates by screen printing with polymer inks. The dimensions of printed structures were measured with optical method as well as by stylus method and experimental results were compared with theoretical dimensions. The values of electrical resistance of thick film layers were measured and evaluated too. Attention is paid to influence of size (width) of path on accuracy of defined dimension furthermore. Investigation is concerned to questions how the printed layer is spread to side out of defined path and what looks the profile of layer after curing process among other.

This article deals with solderability and aggression comparison of several types of fluxes. In our experiments we compare four fluxes (flux R, flux F 1, flux for nickel, and flux for aluminum). For solderability measurement we used wetting balance method. The flux aggression against copper layer was measured on spectrophotometer after the reflow process and it was determined by the measurement of light absorption on spectrophotometer.

The work is focused on diagnostic of polymer thick film layers prepared by screen printing. The conductive silver polymer pastes and resistive carbon black polymer pastes are used for samples preparation. The shape parameters, roughness were analyzed in dependence on viscosity of pastes for screen printing. The process of layer deposition is influenced by many factors among others by viscosity of paste too. Thickness of layer, its roughness, precision of contours of deposited layer defined by screen are depended on process of deposition. Viscosity of thick film pastes was measured by rotational viscometer with different configuration of measured systems. The surface profile of cured layer was scanned by device used stylus method. Shape parameters and roughness were determined for this scanned profile.

Článek se zabývá problematikou vlivu mechanického stresu na pájené spoje, respektive sledováním změny elektrických parametrů pájených spojů z hlediska mechanického namáhání.

The work is focused on joins realised by electrically conductive adhesives. Lower curing temperature is main advantage of adhesives. But electrical and mechanical parameters are worse than for solders. The influence of thermal shocks on properties of joins realized by electrically conductive adhesives were analyzed. The temperature during thermal ageing is changed from room temperature to temperature below freezing point. Electrical resistance and non-linearity of current voltage characteristic were measured. Mechanical strength was measured too.

The work deals with thick film resistors and their properties. The structures of resistive and conductive thick film layers were prepared by screen-printing by polymer thick film pastes. Samples were exposed to accelerated ageing in environment with enhanced temperature and humidity. Tested sample consist of thick film resistors with different width and length. The non-linearity of current-voltage characteristic of resistors was measured. The measured resistor include not only resistive layer but also interface between conductive and resistive layers. The influence such interface is analyzed.

The presented work is concerned with problems of contact of thick film layers. The samples with structures of two different layers were prepared. Conductive and resistive path were deposited by polymer thick film pastes by Screen-print technology. Silver paste was used for conductive layers and carbon black paste for resistive layers. The contact resistance in interface of two layers represents parameter for quality evaluation. The three-wire method was used for measurement of contact of conductive and resistive layers. The influence of combination of different materials of conductive and resistive layers on contact quality was investigated.

The work is focused on investigation of behavior of thick film resistors. The changes of parameters of thick film samples exposed to accelerated ageing were analyzed. The samples were exposed in three types of environment during relatively long time. The samples with different sizes of thick film resistors were prepared. Conductive and resistive structures were deposited on corundum substrates by screen printing. The silver polymer paste for conductive layer and the carbon black polymer paste for resistive layer were used. The resistance and non linearity of current-voltage characteristic were measured. Non linearity was measured as distortion of sinusoidal AC powering signal.

The investigation of conductive and resistive layers interface is topic of the work. Layers of measured structure were deposited by screen-printing of polymer pastes. The measured structure consists of contact area with different geometry. Contact resistance of interface between conductive and resistive layers was measured as a parameter of quality. The three-wire method was used for measurement. Experimental results were analyzed in the context of contacts geometry and frequency of powered signal.

The work is focused on thin film technologies especially on sputtering of dielectric thin film layers. The AlN dielectric layer was prepared by reactive high frequency sputtering from aluminum target in nitrogen atmosphere. Dielectric layers were deposited at different conditions of sputtering. The power plasma generator and time of sputtering were changed in useful range. Part of work is concerned to investigation of dependence of electrical capacity of thick film capacitors on thickness of dielectric layer. Thickness and thus electrical capacity are depending on distance between target and substrate. Thickness of dielectric layer was measured by using of confocal microscope.

The work is focused on investigation of electrical properties of contact between conductive and resistive thick film layers.

Technologies and processes concerning to preparation of thin film layers are the topic of work. Experimental part of work is focused on analysis of properties of dielectric corundum layers.

The work is focused on investigation of properties of thin film layer in dependence on deposition process.

The work is focused on analysis of interface of two different thick film layers. Contact resistance between conductive a resistive layers was measured and analyzed. Contact resistance is influenced by technology of deposition of layers, by conditions of curing, by materials and surface quality of substrate etc. Three point methods is used for measuring of contact resistance. This parameter was analyzed in dependence on geometry of contact area. Polymer thick film pastes were used for preparation of samples.

The work is focused on problematic of thin film dielectric layers prepared by sputtering technology. The dielectric layer made from corundum and aluminum nitride were prepared and analyzed. Dependence of properties (capacity) on parameters of technological process of deposition of layer was analyzed. Sputter deposition of dielectric layers is realized by sputtering at high frequency.

The aim of this paper is an analysis of the change of thick film resistors' parameters in influence of ambient, where are the specimens operated.

The article is focused on properties of polymer paste materials these were applied in electronics production. Samples of electrically conductive adhesives and electrically conductive pastes for screen printing were chosen for experiment. The dependence of viscosity on temperature was analyzed.

Práce je zaměřena na vlastnosti spojů realizovaných elektricky vodivými lepidly. Analyzovány byly elektrické a mechanické parametry v závislosti na tepelném stárnutí. Teplotní cyklování bylo provedeno při teplotách pod bodem mrazu.

Changes of Properties of Ahesive Joints caused by their cyclic shock exposition at low temperature have been examined. Significal changes in dependence on the number of thermal shocks have been found.

Jsou uvedeny techniky diagnostiky elektricky vodivých adhezních spojů. Z elektrických vlastností jsou sledovány odpor, nelinearita a šum.

The paper is focused on electrical and mechanical properties of joints realised by electrically conductive adhesives. The changes of properties due to thermal cycling was investigated.

The work is focused on analysis of properties of thick film layers, influence of trimming process particularly.

The paper is focused on study of dependence of nonlinearity of C-V characteristic of thick film resistors. the relationship between nonlinearity and topology of resistors was found with using approximation of measured dependences. The experimental results were compared with theoretical relationships.

Příspěvek se zabývá vlivem trimování na vlastnosti tlustovrstvých struktur

Nelinearita tlustovrstvých odporů